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:mod:`Bastion` --- Restricting access to objects
================================================
.. module:: Bastion
:synopsis: Providing restricted access to objects.
.. moduleauthor:: Barry Warsaw <bwarsaw@python.org>
.. versionchanged:: 2.3
Disabled module.
.. warning::
The documentation has been left in place to help in reading old code that uses
the module.
According to the dictionary, a bastion is "a fortified area or position", or
"something that is considered a stronghold." It's a suitable name for this
module, which provides a way to forbid access to certain attributes of an
object. It must always be used with the :mod:`rexec` module, in order to allow
restricted-mode programs access to certain safe attributes of an object, while
denying access to other, unsafe attributes.
.. % I'm concerned that the word 'bastion' won't be understood by people
.. % for whom English is a second language, making the module name
.. % somewhat mysterious. Thus, the brief definition... --amk
.. % I've punted on the issue of documenting keyword arguments for now.
.. function:: Bastion(object[, filter[, name[, class]]])
Protect the object *object*, returning a bastion for the object. Any attempt to
access one of the object's attributes will have to be approved by the *filter*
function; if the access is denied an :exc:`AttributeError` exception will be
raised.
If present, *filter* must be a function that accepts a string containing an
attribute name, and returns true if access to that attribute will be permitted;
if *filter* returns false, the access is denied. The default filter denies
access to any function beginning with an underscore (``'_'``). The bastion's
string representation will be ``<Bastion for name>`` if a value for *name* is
provided; otherwise, ``repr(object)`` will be used.
*class*, if present, should be a subclass of :class:`BastionClass`; see the
code in :file:`bastion.py` for the details. Overriding the default
:class:`BastionClass` will rarely be required.
.. class:: BastionClass(getfunc, name)
Class which actually implements bastion objects. This is the default class used
by :func:`Bastion`. The *getfunc* parameter is a function which returns the
value of an attribute which should be exposed to the restricted execution
environment when called with the name of the attribute as the only parameter.
*name* is used to construct the :func:`repr` of the :class:`BastionClass`
instance.
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